It is well-known that acetylated monoglycerides from the molten state by ordinary cooling to about room temperature solidify into waxy, rather than greasy, polymorphic forms, having great flexibility and stretchability and which further exhibit reduced permeability to water vapor (Feuge et al., Journal American Oil Chemists Society, 1952, 29, 11-14).
Due to these unique properties, some acetylated monoglycerides, especially those of saturated fatty acids, have been used or suggested for use as protective coatings for food products.
U.S. Pat. No. 2,615,159 (issued Oct. 21, 1952) describes the waxy translucent alpha- and sub-alpha forms of unsymmetrical triglycerides in which one of the acid residues are radicals of fatty acids having 12 to 22 carbon atoms and the two adjacent acid residues are radicals of fatty acids having 2 to 4 carbon atoms, namely, acetic acid, propionic acid, or butyric acid.
Further, the solid triglycerides, having melting points from 30.degree. C. to 37.degree. C. and predominantly comprising 1-palmityl-2,3-diacetin or 1-stearyl-2,3-diacetin, are suggested as food ingredients.
U.S. Pat. No. 2,615,160 (issued Oct. 21, 1952) discloses mixtures of symmetrical and unsymmetrical diacetyl triglycerides, being in a waxy translucent form of great stability, in which the non-acetyl residues are radicals of fatty acids having 12 to 22 carbon atoms. The mixtures are substantially free from monoglycerides, diglycerides, glycerol, fatty acids, triacetin, and triglycerides containing no acetyl groups. A process for preparing the diacetyl triglycerides is also described, e.g., exemplified by the hydrogenated diacetyl triglyceride derived from rapeseed oil. The waxy translucent form, melting from 31.degree. C. to 38.degree. C., was obtained on cooling the melted material. Without disclosing any specific teachings U.S. Pat. No. 2,615,160 suggests that those diacetyl trigtycerides with melting points above room temperature, but below body temperature, are suitable as coatings for edible products such as fruits, cheese, preserves, and frozen meats.
U.S. Pat. No. 2,745,749 (issued May 15, 1956) concerns acyiated monoglycerides, e.g., acetylated monoglycerides obtained by acetylation of mixtures essentially consisting of glycerol monostearate, glycerol monopalmitate or mixtures hereof. This reference also states that these acetylated monoglycerides have many potential food applications such as coatings for meat products, candies, ice cream bars and cheese.
M. E. Zabik and L. E. Dawson, Food Technology, 1963, 17, 87 to 91, describe the effect of acetylated monoglyceride coatings on cooked poultry during fresh and frozen storage.
G. F. Luce, Food Technology, 1967, 21, 48 to 54, reviews various methods for the application of acetylated monoglycerides in coating food products, such as meat cuts, poultry, sausages, sea foods, small fruits, and nuts. The coating of cheese is not mentioned.
However, despite these early disclosures and proposals, acetoglycerides per se have failed to become of any practical importance as a coating material for cheese.
Presumably, this is due to the fact that only commercially available acetoglycerides have attracted attention, i.e., acetoglycerides derived from saturated, partly saturated or unsaturated triglycerides containing predominantly C.sub.16 to C.sub.18 or lower fatty acids and melting at temperatures of up to about 45.degree. C. Such acetoglycerides take too long to solidify and are rather soft and greasy, properties that make them unsuitable as coating materials for cheese and other food products, especially as a coating to be peeled off by the consumer before consumption of the food product.
The prior art has suggested ways to overcome these deficiences. All suggestions so far relate to the use of acetoglycerides in conjunction with other coating materials, such as waxes, mineral paraffins and/or synthetic polymers.
Thus, U.S. Pat. No. 3,000,748 (issued Sep. 19, 1961) describes a coating composition for foodstuffs comprising a mixture of an acetoglyceride in which one of the acid residues is a radical of a long-chain unsaturated fatty acid of from 10 to 30 carbon atoms and a cellulose ester derivative, and U.S. Pat. No. 3,388,085 (issued Jun. 11, 1968) describes a coating composition consisting of ethylene-vinylacetate copolymer dissolved in a liquid fully acetylated monoglyceride.
Several patents disclose similar compositions for coating food products in particular meat products. These include FR-A-1,453,977, DE-A-2,030,429 (published Dec. 30, 1971), DE-A-2,222,280 (published Nov. 15, 1973), DE-A-2,324,936 (published Dec. 5, 1974), DE-A-2,411,058 (published Sep. 11, 1975), and EP-A-037,086 (published Oct. 7, 1981).
EP-A-141,299 (published May 15, 1985) discloses a process for the coating of cheese wherein the cheese to be coated in a first step is covered with a layer of an acetic acid ester of monoglycerides of hydrogenated fatty acids whereupon the so coated piece of cheese in a second step is coated with a layer of wax consisting of a mixture of lowmelting microcrystalline waxes and plastic paraffins. Preferred acetoglycerides are those having a degree of acetylation in the range of 0.5 to 0.7 and which contain groups of saturated fatty acids, in particular stearic and palmitic acids. Such products are commercially available and are characterized by having melting points (dropping points) in the range of 35.degree. to 40.degree. C. A drawback of this method is the tendency of the first applied and low-melting acetoglyceride layer to melt off during the second coating step, resulting in an uneven coating having "icicles" and admixture of paraffins and acetoglyceride making this method impractical to apply from a technical point of view. Furthermore, data has indicated definite or probable toxicity of mineral hydrocarbons. Thus, there seems to be a health risk by using mineral hydrocarbons in cheese coating compositions either by intake through direct consumption or resulting from eating cheese into which these mineral hydrocarbons have migrated.
EP-A-403,030 (published Dec. 19, 1990) relates to a method for coating cheese wherein there is used a coating composition comprising a mixture of a triglyceride wherein one or two of the acid residues are radicals of aliphatic carboxylic acids having 1 to 6 carbon atoms and the other acid residues are radicals of saturated fatty acids having 14 to 22 carbon atoms, and a wax or wax-like component which is not of mineral origin and having a melting point (dropping point) higher than that of the triglyceride in the range of 60.degree. to 110.degree. C. Coating preparations containing acetylated mono/diglycerides with a degree of acetylation of 0.5 to 0.7 and melting points (dropping points) from 35.degree. to 40.degree. C. are specifically disclosed.
However, due to partial miscibility and/or polymorphic behavior of the components, such binary mixtures often have complicated melting and solidification characteristics resulting in melting/solidification which takes place over a broad temperature range. This means that the coating needs a long time to cool to obtain sufficient strength. Dropping points do not disclose such behavior. By means of differential scanning calorimetry (DSC) it is possible to elucidate melting/solidification of such mixtures. For example, it appears that a liquid mixture comprising 70 percent of acetylated monoglycerides with a degree of acetylation of 0.7 and 30 percent stearic acid on solidifying exhibits two distinct crystallization (exothermic) peaks at 43.degree. C. and 33.degree. C. A similar behavior, with crystallization peaks at 55.degree. C. and 32.degree. C., is observed during solidification of a mixture comprising 60 percent of acetylated monoglycerides with a degree of acetylation of 0.6 and 40 percent glyceryl monostearate, and a mixture comprising 55 percent acetylated monoglyceride with a degree of acetylation of 0.6, 40 percent hardened vegetable fat, and 5 percent carnauba wax resulting in three crystallization peaks at 60.degree. C., 36.degree. C. and 30.degree. C. Thus, the disclosed coating compositions in the above-mentioned European Patent Application are not all suitable as cheese coatings.
In summary, it can be stated that the solutions presented in the prior art discussed above as regards the efforts of obtaining a coating composition for cheese are not effective.
In view of the above-mentioned state of the art it would be most desirable to provide a cheese coating composition being relatively high-melting and having transitory and distinct solidification and which is not based on the presence of mineral paraffins, waxes, or synthetic polymers.
An object of the present invention is to provide such a coating composition which further has such mechanical properties that the coating composition when applied to the cheese gives effective protection against external contamination, loss of moisture and physical damage, and which is easy to remove by the consumer.
A further object of the present invention is to provide a method of producing protective coatings on cheese using the coating composition of the present invention and a body of cheese coated with the composition.